Saturday's quake happened at about 2:10 a.m. local time, with an epicenter about 203 miles east-northeast of Tokyo, the USGS said. The quake hit at a depth of about six miles.

The Fukushima prefecture was where a 9.0 magnitude earthquake and subsequent tsunami damaged several nuclear reactors in March 2011. More than 15,000 people were killed in that quake and tsunami, and material damage related to the incident was estimated to be about $300 billion.